Improve the quality of ensiled brewers’ grains by pressing raw material and including additives

Wet brewers' grains (WBG) are a by-product of the beer production process used in ruminant feeding, which requires suitable conservation strategies given the high moisture content. The present work aims to evaluate the ensiling process and nutritional quality of silages obtained from brewers' grains mechanically pressed (PSS, 34.1 % of DM) or not (WET, 22.4 % of DM). Both fractions were lab-scale ensiled with no addition (CTR), inoculated with a commercial starter (INC, 2.5 ×105 CFU/g), or added with propionic acid (PRA, 0.5 % fresh matter). The pH, ammonia, and weight losses were monitored at 3, 9, and 27 days, whereas the fermentative profile was assessed after 27 days. The in vitro rumen NDF degradability at 48 h (NDFD 48) and the rumen degradable protein (CPd) was evaluated on final silages. The PSS samples showed a higher pH after ensiling (4.23 vs 3.89), mainly due to a lower lactic acid concentration (16.2 vs 25.2 g/kg DM). The PRA addition lowered the pH in both WET and PSS before ensiling and enhanced the final quality of silage in WET and PSS, whereas the inoculation with commercial starter improved the silage quality only in PSS. The NDFD 48 of all the WBG samples was similar, with an average value of 40.2 %, while the CPd reached an average value of 21.9 %. Overall, the mechanical pressing coupled with additive addition, particularly propionate, can be a practical solution to preserve brewers’ grains.